This synthesis provides an overview of academic findings on the sources of violence in post-war environments and on the strategies to address them. It distinguishes between unaddressed pre-war tensions, war-induced cleavages, and peace-generated conflicts. It shows that, according to the best research, current peacebuilding strategies have two major weaknesses. First, they neglect the micro-level dynamics of violence. Second, they do not devote sufficient attention and resources to state reconstruction (which is distinct from merely holding elections). These weaknesses explain why peacebuilding efforts often fail to end violence even when they produce other positive outcomes.